1. Field of the Invention
The present invention relates to a liquid ejecting head for ejecting a desired liquid using generation of a bubble by applying thermal energy to the liquid, a head carriage using the liquid ejecting head, a liquid ejecting device, a liquid ejecting method, and a recording method. It further relates to an ink jet head kit containing the liquid ejecting head.
More specifically, the present invention relates to a liquid ejecting head having a movable member which is displaced using generation of a bubble, and a head cartridge using the liquid ejecting head, and a liquid ejecting device using the same. The present invention further relates to a liquid ejecting method and recording method for ejecting the liquid by displacing the movable member using the generation of the bubble.
The present invention can be applied to a printer for performing a recording operation with respect to a recording medium consisting of, e.g., a paper material, thread, fiber, textile, leather, metal, plastic resin, glass, wood, or ceramic material, a copying machine, a facsimile apparatus having a communication system, a device such as a wordprocessor having a printer unit, and an industrial recording apparatus constituted by a combination of various processing devices.
In this specification, "recording" means not only forming an image having a specific meaning, e.g., a letter or graphic pattern, but also includes forming an image having no specific meaning, e.g., a pattern.
2. Related Background Art
An ink jet recording method of so-called bubble jet type is known in which an instantaneous state change resulting in an instantaneous volume change (bubble generation) is caused by application of energy such as heat to the ink, so as to eject the ink through the ejection outlet using the force resulted from the state change by which the ink is ejected to and deposited on the recording medium to from an image. As disclosed in U.S. Pat. No. 4,723,129, a recording device using the bubble jet recording method comprises an ejection outlet for ejecting the ink, an ink flow path in fluid communication with the ejection outlet, and an electrothermal transducer as an energy generation means disposed in the ink flow path.
Such a recording method is advantageous in that, a high-quality image can be recorded at high speed and with low noise, and a plurality of such ejection outlets can be positioned at a high density, and therefore, a small-size recording apparatus capable of providing a high resolution can be provided, and color images can be easily formed. Therefore, the bubble jet recording method is now widely used in printers, copying machines, facsimile apparatuses or other office equipment, and for industrial systems such as a textile printing device or the like.
As the bubble jet technique has been widely used for products in various fields, various demands have recently arisen as follows.
For example, an improvement in energy efficiency is demanded. To meet the demand, the optimization of the heat generating element such as adjustment of the thickness of the protection film is studied. This method is effective in that a propagation efficiency of the generated heat to the liquid is improved.
In order to provide high-quality images, drive conditions have been proposed by which the ink ejection speed is increased, and/or the bubble generation is stabilized to accomplish better ink ejection. As another example, from the viewpoint of increasing the recording speed, flow path structure improvements have been proposed by which the rate of liquid filing (refilling) into the liquid flow path is increased.
Of these flow path forms, the flow path structure shown in FIGS. 1A and 1B is disclosed in Japanese Laid-Open Patent Application No. 63-199972 and the like. The flow path structure and the head manufacturing method disclosed in this publication have been invented in consideration of a back wave (a pressure propagating in an opposite direction to an ejection outlet, i.e., pressure propagating toward a liquid chamber 12). This back wave is known as loss energy because this energy does not propagate in the ejection direction.
The invention shown in FIGS. 1A and 1B discloses a valve 10 separated from an area where a bubble is formed by a heat generating element 2, and located at the opposite side to an ejection outlet 11 with respect to the heat generating element 2.
Referring to FIG. 1B, this valve 10 is manufactured by a method using a plate material or the like such that the valve 10 is adhered to the ceiling of a flow path 3 at the initial position, and hangs down into the flow path 3 upon generation of a bubble. This invention is disclosed as a technique of suppressing the energy loss by controlling part of the above back wave using the valve 10.
As is apparent from consideration of a case wherein a bubble is generated in the flow path 3 holding a liquid to be ejected, in this structure, suppression of part of a back wave by means of the valve 10 is not practicable in terms of liquid ejection.
As described above, a back wave itself is not directly associated with liquid ejection. As shown in FIG. 1A, when this back wave is generated in the flow path 3, part of the pressure generated by a bubble which is directly associated with ejection has already allowed the liquid to be ejected from the flow path 3. As is apparent, therefore, suppression of part of the back wave does not greatly influence ejection.
On the other hand, in the bubble jet recording method, heating is repeated with the heat generating element contacting the ink, and therefore, a burnt material is deposited on the surface of the heat generating element due to scorching of the ink. However, the amount of the deposition may be large depending on the kind of ink. If this occurs, the ink ejection becomes unstable. Additionally, even when the liquid to be ejected is the one easily degraded by heat or even when the liquid is the one with which the bubble generation is not sufficient, the liquid is desired to be properly ejected without any property change.
Japanese Laid-Open Patent Application Nos. 61-69467 and 55-81172 and U.S. Pat. No. 4,480,259 disclose that different liquids are used for the liquid generating the bubble by the heat (bubble generation liquid) and for the liquid to be ejected (ejection liquid). In these publications, the ink as the ejection liquid and the bubble generation liquid are completely separated by a flexible film of silicone rubber or the like so as to prevent direct contact between the ejection liquid and the heat generating element while the pressure resulting from the bubble generation of the bubble generation liquid propagates to the ejection liquid by the deformation of the flexible film. With such a structure, deposition on the surface of the heat generating element is prevented, or the degree of freedom in selecting an ejection liquid is increased.
However, with this structure in which the ejection liquid and the bubble generation liquid are completely separated, the pressure by the bubble generation is caused to propagate to the ejection liquid through the expansion-contraction deformation of the flexible film, and therefore, the pressure is absorbed by the flexible film to a quite high degree.
In addition, the deformation of the flexible film is not so large, and therefore, the energy efficiency and the ejection force are degraded although the some effect is provided by separating the ejection liquid from the bubble generation liquid.
As a gradation recording method, Japanese Patent Publication No. 62-48585 discloses a method of changing the size of an ink droplet to be ejected by driving a plurality of heat generating elements, which are arranged in one liquid flow path to be driven independently, at desired timings.
In this publication, two heat generating elements are arranged in one flow path to be driven independently. In this case, when the elements are driven at the same timing, the resultant bubble has the maximum volume. As the timings are shifted from each other, the volume decreases. With changes in the size of an ink droplet, gradation is obtained.